Example Purchase request JMS & MDB. Example Purchase request. Agenda. Purpose. Solution. Enterprise Application Development using J2EE

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1 Enterprise Application Development using J2EE Shmulik London Lecture #8 JMS & MDB Example Purchase request Consider an online store A customer browse the catalog and add items to his/her shopping cart At the backend the customer is interacting with a stateful session bean that holds the items and the customer details During check-out the customer provides payment method and other details Agenda Need for asynchronous processing oriented middleware JMS Java Service MDB Driven Bean Example Purchase request Upon confirmation the backend system has to perform several tasks Create an order update the inventory Send a mail with the order details We want the customer to get a quick response Recall that beans are not allowed to create threads Purpose Solution Allows asynchronous processing of requests by server side components purchasecart() queue Order Bean Inventory Manager Shopping Cart Stateful session bean Purchase Processor MDB Mailer Bean 1

2 Driven Beans A message driven bean (MDB) is an enterprise bean that process asynchronous messages EJB defines JMS (Java Service) as the Messaging API for MDBs We ll describe JMS briefly and then return to Driven Beans Messaging Domains Publish/subscribe (pub/sub) subscribe to a Topic A message sent to a certain topic will be routed to all subscribers of that topic Point-to-point (PTP) register to a A message sent to a queue will be routed only to one of the registered consumers Often a single pair of producer/consumer per queue, hence the name PTP JMS Java Service Publish/subscribe Java API for asynchronous messaging Standard, vendor-neutral Like JNDI, JDBC and many others APIs divided into an API and SPI (Service Provider Interface) Defined jointly with partners Wide acceptance as standard Built in mind with a lot of industrial experience Topic A Topic B Broker What are MOMs? Oriented Middleware Point-to-point Broker IBM MQSeries, BEA Tuxedo, SonicMQ, Broker 2

3 Advantages of MOMs Loosely coupled Reliable Asynchronous High performance JMS Terminology Destination Topic / Producer / Consumer Guaranteed Delivery Broker Usage (1) Durable queues/topics Guaranteed/certified delivery Store-and-forward 1 Acquires a reference to the using JNDI JNDI Service Questions? 2 Use the to create a Usage (2) 3

4 Usage (3) Usage (6) 3 Use the connection to create a 6 Send or receive a message Producer Usage (4) Sample client 4 Lookup the JMS destination () using JNDI public static void main(string[] args) { try { Context context = new InitialContext(); Topic factory (Topic)context.lookup( javax.jms.topic ); Topic connection = factory.createtopic(); Topic session = connection.createtopic( false,.auto_acknowledge); Usage (5) Sample client 5 Use the session to create a Producer or Consumer (use destination as argument) Producer Topic topic =(Topic) context.lookup( weather ); TopicPublisher publisher = session.createtopicpublisher(topic); Text message = new Text(); message.settext( It is going to be Sunny ); publisher.publish(message); connection.close(); catch (JMSException jmse) { jmse.printstacktrace(); 4

5 Sample consumer Questions? public class SampleListener implements Listener { public void on( message) { Text text = (Text)message; String text = text.gettext(); System.out.println(text); Topic vs. Establishing a queue session is exactly the same using corresponding constructs Parent Interface Destination Producer Sender Point-to-point Topic Topic Pub/sub Topic Topic TopicPublisher Text Map Object Stream Byte types Consumer Receiver, Browser TopicSubscirber Sample consumer public static void main(string[] args) { try {... create Topic and Topic as for... producer TopicSubscriber subscriber = session.createsubscriber(topic); Listener listener = new SampleListener() subscriber.setlistener(listener); connection.start();... catch (JMSException jmse) { jmse.printstacktrace(); Relation with EJB All types of beans can send JMS message beans and Entity beans cannot receive JMS messages as the reception is asynchronous and they cannot start a new thread EJB include the bean type - Driven Bean to allow asynchronous processing of messages 5

6 Developing MDBs No need for Remote/Local interfaces, only bean class MDBs are stateless simple life cycle Only a single generic business method - on Developing MDBs The bean can be used both with a Topic or a The details about the connection factory is given in the deployment descriptor The destination (Topic or ) is specified in a server specific manner Purchase Processor example PurchaseProcessor activationconfig = propertyname= destinationtype propertyvalue= javax.jms. propertyname= destinationname propertyvalue= jms/purchase ) ) public class PurchaseProcessorBean implements Listener { public void on( message) { //... Process the message Does Not Exist newinstance() removed Pooled on() Developing MDBs You don t need to create connections, sessions, etc. Creates the connections and sessions It creates a pool of instances of your bean, create subscribers for them and set them as listeners You only need to implement the on() method Additional topics Transactions Filters, message types, acknowledgement <message-selector> pit-falls ordering, poison messages, return results 6

7 Questions? 7